The employee was cutting 2"" x 2"" x 1/4"" square tubing for handrail supports and catwalk structure. The employee had cut three pieces 3'6"" long. Each stick weighed approximately 19 pounds. The employee grabbed three sticks of the tubing and carried them up the stairs to the catwalk. As EE was walking up the steps EE felt a pain in EE's lower back.